Incidents of Repetitive Strain Injuries (RSI), for example Carpal Tunnel Syndrome (CTS), are increasing at an astronomical rate, affecting nearly two million workers annually and costing an estimated $20 billion per year in workers' compensation, medical benefits, and lost wages. RSI to the upper extremities results, in part, from the repetitive reaching, stretching, bending, flexing, and twisting of fingers. Maintaining the wrist in an awkward position during these repetitive motions increases the likelihood of injury. Over time, these awkward repetitive motions can inflame soft tissue, creating pressure on various nerves and causing pain, numbness, and tingling sensations in the upper extremities. Unless treated, RSI may result in pain, numbness, weakness, and loss of dexterity due to pressure on the median nerve.
The group most affected by RSI is keyboard operators such as secretaries, data entry personnel, computer programmers, call center customer service employees, and journalists. From the standpoint of typing speed, keyboards have advantageously evolved to the point where pauses in typing, formerly required in older model typewriters for carriage returns, paper feeds, and manual error corrections, are no longer required. While disadvantageous from an efficiency standpoint, these typing pauses significantly reduced strain and fatigue on the fingers, wrists, lower arms, upper arms, shoulders, neck, and back. Consequently, this reduced the occurrence of CTS and other repetitive strain injuries.
Despite the increased efficiency of the keyboard, the evolution of the keyboard from an ergonomic and health standpoint has been largely overlooked. With a conventional keyboard, the palms “float” in the air or rest on the desk in front of the keyboard and the wrist and fingers bend upward to depress the keys. Consequently, the muscles and tendons in the lower arm, neck, and shoulders must continually support the fingers at this upward angle to prevent the fingers from inadvertently striking the keys. Maintaining this position while typing for an extended period of time can strain the muscles and tendons of the lower arm, neck, and shoulders and significantly contributes to CTS and other repetitive strain injuries.
Additionally, many keyboards today have a non-linear relationship between the force applied to a key relative to the downward distance a key travels during a key stroke. That is, in order to prevent inadvertent key striking, many keyboards require a relatively large force to initiate a key stroke, but require a relatively small force on the keyboard key for the remainder of the stroke. The result is that often a greater force than necessary is applied to a key during the latter portion of the key stroke, and the abrupt end of the stroke results in an impact or shock on the fingers. While this effect is relatively insignificant in striking a single key, the cumulative effect of these forces and shocks from continuous typing can aggravate nerves and soft tissue in the upper extremities to the point that CTS and other repetitive strain injuries can occur.